Temperature-indicating device



I Dec. 16, 1930. P. G. wATERLoo 1,785,562

TEIPEHATURE I NDI CATI NG DEVI CE Filed May 9. 1928 Pauz G. Wairzao INVENTOR ATTORNEY Patented Dec. 16, 1930 PAUL GEORGE WA'I'EBLOO, OF MADEBA., Plllh'fil'S'YII7A.NIA

TEHPEBATURE-INDIGATING DEVICE Appeamn mea my a, mca. sum no; 276,355.

The temperature indicating devices heretofore used on motor cars to measure the temperature of the water or cooling medium have dependedlupon -fo'r thir operation the expansive properties of mercury, or alcohol when heated'. This has sometimes been a very crude and unreliable method, and also had the disadvantage that they were located on the motor car in such a position that it was sometimes difiicult to obtain a readin My device overcomesthese diflicu ties in that it is more accurate, and reliable due to being electrically operated, and as it may be mounted anywhere such as on the instrument board is more convenient to read. Thus it overcomes the disadvantages of former types.

A particular embodiment of my device is p shown in the accompanying drawings, in

which: a f

Figure 1 is aplan view' ofthe electrical connections.

Figure 2 is'a Sectional Vview through a conductorof a water cooling system, showing the arrangement of one of the resistancestherein.

2* The device consists of two fixed resistances R3, and R4 which are made of a suitable metal which will not changein resistance as their temperature changes.

The resistances RB, and Rftare 90 and 4.2

0 ohms respectively. The resistance Rl is also made of materialv similar to that used Vin the construction of R3, ,and Rtso that its resistance will not change with changes in temperature.4 Rl is a variable resistance and by ues of the other resistances.

The resistances R2, and B are of 2 ohms and 5 ohms respectively. They are made of suitable metal so that their resistance will change with changes of temperatures.

S is an electrical 'battery which energzes the device, 'and on the motor car may be the battery which supplies direct current' to the other electrical devices of the car. It has a potential value of 6 volts which is the potential commonlyused by motor cars. a

V is the indicating device and s of such construction that it responds to very small lneedle or hand of t e indicating device rer changing the value of R1 the device may be compensated for any inaccuracies in the valpotentials. ln the present device the indicatin hand is actuated by the mechanism of a mil ivoltmeter, which has a full 'scale value of 100 millivolts.

In practice the o eration is as follows: Current flows from t e battery S to ints A andv C. At oints A and C it dividds The portion of the current flowing to A asses through resistances R1,R2 and R5, andp from R returns to the negative terminal of the v battery. The portion of the current flowing 00 to point C asses through resistances R3, R4 and R. rom R the current returns to the negative terminal of the battery. Resistance Rl is then adjusted so that the circuit comosed by RI, R2, R3, and R4 is balanced. en this condition of balance is reached no current will flow from point P to point. Q because there is no difference of potential between these two oints. Therefore, the

mains at zero. This condition of balance is assumed to be reached at a temperature of 0 degrees centigrade.

R2 is placed where it comes in contact with the water of the cooling system, and is arranged so that as the temperature of the water rises and falls the temperature of resistance R2 will rise and fall. Resistance R2 is protected from actual electrical contact with the water by a thin brass shell 1 (Fi 2). The heat of the lwater adjacent to therass shell is transmitted to the resistance R2.

The cooling system includes a Sectional conduit 3 connected by a union 4 provided adjacent the ends thereof with o nings to receive the ends of the shell 1 an the latter vincludes a hollow tubular body provided at the ends with angularly dis osed branches fitting within the openings o the union and receives plugs 5 of insulating material carring bindin posts 6 that are connected to t e ends oft e resistance R2 located in the shell 1. The resistance R2 is spaced from the shell 1 and has the ends, thereof extending throughv the angularly disposed branches for connection with the bindin posts.

'The condition of the resistances Rl, R2, R, and Re; at 0 degrees centigrade is one of balance. However, with the heating of i RZ this condition is disturbed, as RZ is concentigrade. Therefore, as the potential between points A and P is equal to the potential between C and Q at a temperature of 0 degrees centigrade; then no current flows between points P and Q through the indicating device V, as there is no difl'erence of potential between these two points to lcause such a fiow of current. With the heating of resistance R2 by the rise in temperature of the water a current fiows from point P to point Q, flowing through the sensitive indicating device' V and causing the indicating device V to register an increase in temperature. This fiow of 'current takes place because resistance R2 is constructed of suitable material whose resistance rises in sympathy with a rise in temperature of the water in the cooling system. It is in accordance with well known physical laws that a resistance constructed of a pure metal such as iron will have its resistance increased when heated. When the resistance of resistance R2 increases, a current flows from point P to point Q, and through the indicating device V. This flow of current is produced because the resistance between points Pl and B has risen. Therefore, the increase of potential between points P and D is able to force a current through the indicating device V and through the resistances fR4 and R to the ne ative terminal of the battery. Therefore,`t e greater the resistance of resistance R2, which increase is caused by the heating eii'ect of the the conduit of cylindrical form, the union having openings in its upper side and adjacent its ends, a hollow tubular body arranged within the union and provided at its ends with upwardly extending branches fitting in said openings in the union, plugs of insulating material fitted in the ends of said branches, binding posts for electrical conductor wires mounted in said plugs, and an electrical resistance element comprising a coil arranged within the said tubular body in spaced relation to the walls thereof and having its terminals extending upwardly through the branches of the body and spaced from said branches and connected with respective ones of the binding posts.

In testimon whereof I afiix my signature.

PAU GEORGE WATERLOO.

water, the greater the current flowin from point P to point Q, the greater will e the temperature indicated by the indicator V.

The function of the resistance R is to keep the voltage constant and thereby also regulating the current flowing through the resistances Rl, RQ, R3, and EA. This is to prevent any changes in voltage of the electrical system of the motor car caused by starting'and stopping of the battery generator, from changing the reading of the temu perature indicatng device V.

The operation of resistance R is as follows: Being constructed of suitable metal, such as iron, an increase in temperature will increase its resistance. Therefore, an increase. in voltage of 'the electrical system of the motorcar will have a tendency to heat the resistance R, thereby making its resistance greater, which has the effect of maintaining the voltage supplied to the resistances Ri, 19.2, 33, and Re at a constant value.

Having described the invention, claim:

In a temperature indicating apparatus for use in connection with internal combustion engines having' a cooling system einbodying a 'water condnit, e union for installation 

